The present invention relates to a nitride semiconductor light emitting device and a method for fabricating the nitride semiconductor light emitting device.
In recent years, various kinds of semiconductor laser devices have been widely used as light sources for optical disk devices. Among others, blue-violet semiconductor laser devices which use III-V nitride semiconductors such as gallium nitride (GaN) are used as light sources for next-generation high-density optical discs (Blu-ray Discs), and are capable of oscillation of light in the short wavelength region (400 nm band) that can be focused to a smaller spot on an optical disc than light in the red and infrared regions. Thus, blue-violet semiconductor laser devices effectively increase reproduction and recording density of optical discs, and are becoming popular and indispensable.
New discs that use blue-violet semiconductor laser devices need highly reliable high-power blue-violet semiconductor laser devices so as to enable higher density and high-speed writing. In AlGaAs- and AlGaInP-based semiconductor laser devices used for conventional CDs (Compact Discs) and DVDs (Digital Versatile Disks), dielectric films (protective films) made of SiO2, Al2O3, etc. are formed on the facets of the cavity to prevent deterioration of and optical damage to the facets of the cavity.
However, in GaN-based laser devices, if protective films made of oxide are formed on the facets of the cavity, the oxygen in the protective films causes the cavity facets to undergo oxidation and/or deterioration.
In light of this, Japanese Laid-Open Publication No. 2007-103814 (which will be hereinafter referred to as “Patent Document 1”) has disclosed that layers made of aluminum nitride, when used as protective films formed on the facets of a GaN-based laser device, allow separation of oxygen from the cavity facets, thereby reducing oxidation-caused deterioration of the facets.
Japanese Laid-Open Publication No. 2007-273951 (which will be hereinafter referred to as “Patent Document 2”) has also disclosed that when films made of aluminum nitride crystals or aluminum oxynitride crystals are used as protective films formed on the facets of a GaN-based laser device, the crystallinity of the protective films is improved as compared to amorphous protective films, thereby suppressing permeation of oxygen into the protective films.